What is Exercise
Stress Test?
Bala N. Aiyer, M.D.
 
   
 

What is an exercise stress test?

An Exercise Stress Test, which is also known as "Exercise Tolerance Test", "Stress EKG" and "Treadmill Test" is performed on a motorized treadmill or sometimes on a bicycle ergometer, to assess the heart's function and its blood supply to determine the exercise capacity of the individual and blockages of the arteries to the heart that can lead to heart attack. It is also performed to evaluate the functional capacity of heart and also about abnormal heart beats in a person already known to have heart disease or had heart surgery.
The principle behind a stress test is simple. Coronary arteries that are diseased, blocked or narrow may function adequately when a person is at rest. When they exercise, they unable to meet the increase in the requirements of the heart for oxygenated blood supply. This results in a characteristic change in the heart's electrical activity. This will be seen in the EKG tracings recorded during several stages of such an exercise or exertion. This may or may not cause a chest pain or angina. The EKG and blood pressures are recorded before, during and after a set pattern of exercise performed on a motorized treadmill or bicycle at varying speed. A healthy person taking the test may feel little or no discomfort while exercising. However, a person who has a heart condition may feel a transient uncomfortable feeling of pressure or pain in the chest or weakness early during the test. This may cause a classical abnormality in the EKG at that time.
 
  
 

Who needs Exercise Test?

There are three major Categories of individuals who may undergo an exercise stress testing and benefit from it. Certain percentage of false positive and false negative outcome of the test has to be kept in mind, like any other medical investigations, based on the age, risk factors, index of suspicion, prevalence in the community and the pretest probability of coronary artery disease, to come to a meaningful consideration of the test results.
[1]: Apparently healthy persons with no significant major risk factors.
[2]: Individuals at a high risk who have indications of possible heart disease or with more than one or two risk factors for heart disease.
[3]: Individuals with known or suspected heart disease who need to be investigated for the treatment and follow up. These will include persons who already had a heart attacks, had heart surgery or has been on medical treatment.
 
 

Apparently Healthy individuals under the age of 45 years can usually begin exercise programs without the need for a doctor's physical examination or an exercise stress testing if they had no known risk factors. An exercise stress testing is of no diagnostic value in this population and is of no use. However, the exercise program should begin at a slow pace and proceed gradually. The individual should also be very alert to look for the development of any unusual signs or symptoms that might indicate an underlying heart problems, like difficulty in breathing, chest pain, dizziness or weakness after a short period of exercise. At or above the age of 45 years, it is desirable to have a maximal exercise stress testing done before beginning an exercise program. It is also desirable for those already exercising, once they reach the age of 45 years.

 
 

Individuals at high risk are those with at least two major coronary risk factors or symptoms suggestive of a heart disease. A stress test prior to beginning a vigorous exercise program is desirable for individuals of any age if they have abnormal EKG or symptoms suggestive of heart disease such as chest pain after normal activity. Individuals over the age of 45 years with two or more risk factors and those between 35 years to 44 years with more than two risk factors for coronary artery disease must undergo a maximal exercise stress test after a thorough physical examination, even if they feel normal and have no symptoms. A maximal exercise testing is desirable in this group of people for diagnosis and early treatment, even if they are not planning an exercise program.

 
 

Individuals with known heart disease should have an exercise stress test done under a physician's supervision. It is helpful to assess the extent of the heart problems, effects of treatment and prognosis and to make plans for further evaluation for treatment. The test must be done prior to starting any vigorous exercise program. This is important to measure the functional capacity of the person, to monitor the progress of the heart condition and to assess the safety of a vigorous exercise program. They should perform only the amount of exercise prescribed by the physician. If any symptoms occur during the exercise, they should get reevaluated by the physician again and may need a stress test.

 
 

Individuals with certain abnormalities of the heart like birth defects of the heart, abnormal and irregular heart beats, with heart valve disease, heart failure, lung problems like bronchial asthma and emphysema and persons with musculoskeletal problems may not be suitable for stress testing and will need evaluation by the physicians. Certain birth defects of the heart are associated with abnormal body growth and appearance including thin, tall stature with long fingers and hands. These individuals will need evaluation including an echocardiogram and may not be suitable for any strenuous exercises or stress testing.

Individuals with certain abnormal heart conduction like bundle branch blocks and those with heart valve diseases are not suitable for exercise stress test. Similarly, individuals with musculoskeletal problems and lung problems will not be able to walk on a tread mill properly. These persons can have stress test and heart imaging studies done by other pharmocological methods to increase the oxygen demand of the heart or increase of heart rate and using radio-isotope imaging of the heart. Results of the exercise stress tests may indicate new problems and may dictate reclassification of the individuals for medical treatment or heart surgery and for an exercise program.

 
  
 

This is how the test is performed.

On the day you are scheduled for the test, you should only eat a light breakfast that morning [not on empty stomach]. You should refrain from coffee, alcohol and cigarettes for at least 4 hours before the test. You should report to the Cardiologist's office [or the hospital where the test is to be performed] in comfortable clothing like pant or shorts and should wear or bring comfortable shoes like sneakers.
Several EKG electrodes are painlessly attached to your chest after cleaning the skin. A blood pressure cuff is wrapped around the arm [usually right arm] to check the blood pressure during the test. EKG, heart rate and blood pressure will be recorded while you are at rest before the test. Then, you will be walking on a motorized treadmill. You begin a slow and steady exercise on the Treadmill. The speed and elevation will be gradually increased every 2 or 3 minutes. During the exercise test the heart rate, EKG and blood pressure are continuously monitored and periodically recorded. The heart rate and blood pressure will gradually increase as you walk on the treadmill.
 
 

This is how long the test will last.

The object of the test is to put a strain on the heart [under controlled condition] to cause symptoms or a change in the EKG pattern to reveal any strain or any underlying heart problems. As the speed and angle [elevation] of the treadmill increases every few minutes you will notice increasing strain on walking though it may appear simple to begin with. As speed increases, you may start jogging as needed. The test will be terminated and the moving belt will be stopped if you reach a target heart rate or stage of exercise or if you developed any significant symptoms or EKG changes. Usually the test may last from 8 to 14 minutes of walking or jogging. Sometimes it may be quite short if you get symptoms or EKG changes or if you are physically not well conditioned though healthy. After the test resting studies are done during recovery for about 8 to 10 minutes. You are free to leave after resting for about 15 minutes.
 
  
 

This is what the outcome might be.

A healthy person taking the test may feel little or no discomfort. A person with a heart condition may notice significant chest pains, weakness or shortness of breath. Severe anxiety alone can cause some of the problems. Sometimes, arthritis or other painful conditions may prevent you from completing the test. An untrained weak person, otherwise healthy, may not be able to walk for too long. It is not a test for your bravery. So, if you notice any discomfort, you should tell the supervising physician to decide if the test should be stopped.
 
 

The test which causes a strain on the heart. There is a very small risk of heart attack or a serious abnormal fast or very slow and irregular heart rhythm. This is why this test is administered under the direct supervision of a Cardiologist and in a place where all the proper test equipment and necessary emergency drugs are available. When the test is completed, it is possible that it could be positive which means that you have a high probability of having significant blockages of the arteries of the heart. This may require further testing like heart catherterization. Based on those findings, one may be advised the need for a balloon angioplasty immediately or a heart bypass surgery or intensive medical treatment for the heart condition. The test can be "Positive" in a person with normal heart and can also be "Negetive" in a person with a heart condition. The Cardiologist will be able to determine the "probability of a persons heart condition and its functioning capacity taking into consideration of various factors in addition to the test.

 
   
 
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